Smart Digital Image Correlation Patterns via 3D Printing

Digital Image Correlation (DIC) is a popular experimental technique for measuring full-field deformations in materials. Accurate motion and displacement field reconstruction in DIC depend heavily on the intrinsic material texture or speckle patterns painted on the material prior to deformation. Many traditional techniques such as spray painting, ink stamping, or manual texturizing have provided adequate performance but are often challenging to apply on highly compliant, porous or non-planar surfaces. To address this challenge we present a new, robust and efficient technique to print DIC speckle dot patterns on both planar and non-planar sample surfaces using a custom-modified 3D printer in an automated fashion. In this new technique, a 3D printer is modified by replacing the conventional extrusion head with a syringe filled with ink. The motion of the 3D printer is controlled via customizable G-code scripts, precisely controlling both the extrusion volume and spatial positioning of the print head in a well-controlled and predictable fashion. The printed speckle dots have radii on the order of O( $$10^2$$ ) $$\upmu$$ m, and the subsequent DIC reconstructed deformations have an accuracy on the order of O( $$10^{-2}$$ ) pixels and O( $$10^{-4}$$ ) in measuring displacements and strains, respectively. Furthermore, we demonstrate that this technique has the capability to print suitable patterns for tracking large and heterogeneous deformations in highly compliant and porous materials, as well as materials with significant 3D topographies.